Electromagnet



A. G. STIMSON ELECTROMAGNET Dec. 16, 1941.

Filed Feb. 18, 1941 Inventor. Allen 6. Stimson, b J m 7&2 His Abtor'nq Patented Dec. 16,. 1941 2,266,618 ELECTROMAGNET Allen G. Stimson, Schenectady, N. Y., assignmto General Electric Com New York pany, a corporation of Application February 18, 1941, Serial No. 379,513

8 Claims.

My invention relates to electromagnets and particularly to the plunger type of electromagnets having provision for exerting a pushing force as well as a pulling force.

Heretofore three types of electromagnets have been well known. The plunger type, shown by way ,of example in Patent 1,696,615 to Trombetta, issued December 25, 1928, has a relatively long stroke and a reasonably constant pull as the air gap decreases. The clapper type of magnet, shown by way of example in Patent 1,761,772 to C. F. Carpenter et 211., issued June 3, 1930, is characterized by relatively small magnetic leakage area, a short stroke, and simplicity and cheapness of construction. The E-shaped type of magnet, shown by way of example in Patent 1,964,464 issued on June 26, 1934, to R. W. Goff tends to combine the characteristics of the clapper and plunger types of magnet. The long stroke of the plunger type of magnet is not, however, characteristic of the E-shaped magnet. In many applications, where a small inexpensive magnet is required to exert a relatively long operating stroke, it is desirable to combine the most desirable characteristics of the clapper and plunger magnets. Such a combined construction should provide the long stroke and relatively constant pull characteristics of the plunger as well as the small leakage area and the reliable and inexpensive construction of the clapper type magnet.

It is, therefore, an object of my invention to provide a highly efficient plunger type of electromagnet of simple, reliable and inexpensive construction having a relatively long stroke.

merit within the central aperture of an energizing solenoid.

For a more complet'eunderstanding of my iii-- vention and a further appreciation of its many objects and advantages reference should now-be had to the following detailed speciflcation and the accompanying drawing in which Fig.1 is a side elevation of an electromagnet embodying my invention; Fig. 2 is a plan view of the electro- ,tionary core of my electromagnet comprises two It is a further object of my invention to provide a plunger type magnet having provision for exerting a pushing as well as a pulling force.

A still further object of my invention is the provision of a clapper type of plunger magnet, the pull characteristics of which may be varied substantially without appreciably altering its construction.

According to my invention, a longitudinally movable plunger is supported for substantially straight line movement upon a pair of pivotally mounted links, and is so arranged that in its closed position it cooperates with a stationary core structure to complete a substantially rectangular magnetic frame. The stationary coreand movable plunger are provided with cooperating pole faces in a plane substantially perpendicular to the direction of movement of the plunger. The plunger is positioned for move- 56 sets of stacked laminations l0 and H of magnetizable material spaced apart by the relatively thick plate I2 of magnetic material to define a pair of central slots. The plate 12 is provided with a mounting flange l3 for attachment to a suitable support. The magnetic core H), II is approximately C-shaped and has an upper horizontal portion which overhangs the lower horizontal portion to form a pole face M.

A movable plunger l5, formed of a solid stack of laminations of magnetizable material, is movably mounted beneath the pole face H for substantially straight line longitudinal movement toward and away from the pole face I 4 and laterally with respect to a second pole face 20 of the core. The pole face 20 is on the lower horizontal leg of the core and is disposed at right angles to the Dole face |4. The cross sectional dimensions of the plunger l5 are slightly less than the dimensions of the pole face I4 for reasons which will appear hereinafter. The plunger i5 is pivotally supported upon a pair of swingable links 2! and 22 which lie within the slotted core to, H and are pivotally mounted upon a rivet, 23 and a bolt 24, respectively, passing through the core l8, H. The links 2| and 22 are U-shaped to follow in general the contour of the core Ni, H, as is best shown at Figs. 3 and 4, and are preferably formed of non-magnetic steel. To accommodate the pivoted ends and the body portions of the links 2| and 22, the plate I2 is recessed as shown in Figs. 3 and 4, and the central laminations of the plunger 15 are likewise recessed as shown. The recessed central laminations of the plunger form at its ends a second pair of slots for receiving the ends of the links 2|, 22. To form a lower limit stop for the plunger ii, a protruding abutment 25 formed on the plate i2 is disposed to engage a otally mounted upon a fixed rivet 23 and the,

link 22 is pivotally mounted upon a removable bolt 24, while the movable plunger i is supported upon the links'2l and 22 by means of a removable bolt 28 and a fixed rivet 29-respectively. The bolts 24 and 28 are provided with nuts 30 and 3| respectively and are removable. The rivets 23 and 29 are provided at their central portions with sleeves 32 and 33 respectively. The sleeves 32 and 33 are of a length equal to the thickness of the plate I2 so that they assist in spacing apart the core portions in and II and the laminations of the plunger Hi, The sleeves also serve as bearings for the links 2| and 22,'

which are thinner than the plate l2 so that they may move freely-in the slots formed between the core portions i0, H and by the recessed central laminations of the plunger it. To provide for the exertion of either a horizontal or a vertical pushing force by the plunger l5, the link 22 is formed with an apertured ear 34 extending beyond the periphery of the core member it. H. In operation the ear 35 rotates about the bolt 24 and may be attached to any desired mechanical load. "Likewise, to provide for the attachment of the armature E5 to a'mechanical load in pulling relationship; the armature I5 is aper-.

tured at;35.

Since my, electromagnet is particularly designed for operation in connection with alternating current, it is desirable to provide a shading coil to minimize the effect of variation in current in the alternating current line. My shading coil comprises a U-shaped copper member 36 embracing the core it, It and havin its ends connected together by the copper rivet 2?. It will be recalled that the copper rivet 21 also serves the purpose of supporting the central lamination 12. With this construction the shading coil in effect shades about three-fourths of the area of the pole face 84.

An energizing winding or solenoid 37 is disposed to enclose the upper portion of the armature l5 and the air gap between the pole faces l4 and 15a. The solenoid 3T fills substantially the entire space between the upper and lower horizontal legs of the cor l0, H and is provided at each end with bifurcated insulating collars 38 and 39. The solenoid is positioned by the pole face l4, which extends a small distance into the solenoid, and by the bifurcated collars which embrace the core ill, H. The solenoid 3! is held firmly in position by an L-shaped wedge 48 having a wedge-shaped flange 4| engaging a notch 42 in the core In, H. The wedge is drawn and held in position by a bolt 43 which passes through a hole in the core I, H and is threaded into the plate i2. For connection to a source of energy the solenoid 31 is provided with terminals 44 and 45. The function of the removable bolts 24 and 28 will now be apparent. By removing the bolts the plunger l5'may be swung away from the pole face '20 to permit removal of the solenoid 31. It will now be evident that the difference in sectional dimensions of the pole face l4 and the plunger l5 permits the solenoid 31 to I be positioned by the pole face while insuring clearance between the solenoid and plunger.

The lower end of the armature I5 is biased away from the pole face 20 of the core by a tension spring 45 secured at one end to a fixed support 41 which may be the same support upon which the flange I3 is mounted.

In operation, when the armature 15 picks up it moves in an arcuate path of relatively large radius defined by the movement of the bolt 28 and the rivet 29 in arcs about the rivet 23 and the bolt 24, respectively, as centers. The pole face it and the abutment 25 are so positioned that the armature moves over center with respect to the rivet 23 and the bolt 24; that is, at about the midpoint of the path of movement the armature l5 lies tangent to the arcs defined by the bolt 28 and the rivet 29. Since the radius of these arcs is large with respect to their lengths, it will be seen that the armature 55 moves in substantially a straight line toward the pole face 83. It will be observed that when the core and armature are energized an attractive force will be exerted between the pole face 20 of the stationary coreand the side of the armature l5. Whenever the bolt 28 is below dead center with respect to the rivet 23 this horizontal force will have a downwardly directed vertical component opposing. the pickup force exerted upon the armature from the pole face Il, and whenever the bolt 28 is above dead center an upwardly directed vertical component of force will assist the pick-up force from the pole face It. It is for the purpose of neutralizing the attraction between the'pole face 29 and the side of the armature that the tension spring 46 is arranged to exert an oppositely directed force upon the armature. Furthermore,

since the spring, 46 is disposed for overcenter operation, it has the effect of assisting the electromagnetic pull on the lower half of the stroke and opposing the electromagnetic pull on the upper half of the stroke. Thus the vertical components of forc exerted by the pole face it in directions tending to exaggerate the increased pull as the armature approaches the pole face M are neutralized by the spring 46; and the spring also introduces vertical components of force in opposite directions to make the pull curve more constant.

If desired, of course, my electromagnet may be used without the spring 46. a The effect of the spring 46, however, is such that by its use an adjustment of the pull of the solenoid is possible without altering its construction substantially. The magnetic pull may be adjusted by changing the tension of the spring 46, since the spring exerts a vertical component of force upon the plunger.

It will now be apparent that my electromagnet has a long stroke, reliable and inexpensive construction, and high efiiciency. The concentration of all the core iron in a single C-shaped core section has the effect of increasing the emciency of the magnet over that of a double-cored plunger magnet. of the core increases as the square of the sectional dimensions, while the surface area of iron increases directly with the dimensions, a single core section of large cross section will have less leakage area than two core sections having the same total cross section. Tests of the instant electromagnet have proven that'it can exert substantially twice the pull of a double-cored magnet of the same size.

While I have described but one preferred em- Since the cross-sectional area 7 bodiment of my invention, it will be of course, by those skilled in the art that many modifications thereof may be made, and I,

therefore, wish to have it understood that I in tend in the appended claims to cover all such modifications as fall within the true spirit and gap, said means comprising a swingable linkmovable within said slots and pivoted to said core and to said plunger, and an energizing winding disposed in magnetizing relation to said core and plunger.

2. An electromagnet comprising a divided stationary core of magnetizable material mounted upon opposite sides of a recessed central plate of magnetic material to define a first pair of slots, a movable plunger centrally recessed to define a second pair of slots, means for supporting said plunger from said core to define'therebetween an air gap and to provide for substantially straight line longitudinal movement of said plunger to close and open said air gap, said means comprising a plurality of swingable links movable within said pairs of slots and pivoted to said core and to said plunger, and an energizing solenoid disposed in the region of said air gap to magnetize said core and plunger.

3. An electromagnet comprising a divided stationary core of magnetizable material of substantially c-shape having an overhanging upper horizontal leg forming a pole face, a recessed plate disposed between the halves of said core to space said halves apart and thereby to define a first pair of slots, a movable plunger disposed in a position beneath said pole face to define therewith an air gap, the opposite ends of said plunger being centrally recessed to form a second pair of slots, a pair of swingable links pivotally attached to said core within said first pair of slots and pivotally attached to said plunger within said second pair of slots for supporting said plunger in said position and for substantially straight line longitudinal movement to close and open said air gap, and an energizing winding enclosing said air gap and a portion of said movable plunger.

4. An electromagnet comprising a divided stationary core of magnetizable material of substantially c shape having an overhanging upper horizontal leg forming a pole face, a recessed plate of magnetic material disposed between the halves of said core to space said halves apart and thereby to define a first pair of slots, said plate being provided with a mounting flange extending beyond said core and being also provided with a protruding abutment lying within one of said slots, a movable plunger of magnetizable material disposed in a position beneath said pole face to define therewith an air gap, the opposite ends of said plunger being recessed to form a second pair of slots, a pair of swingable links movable within said first and second pairs 01! slots for supporting said plunger in said position and for substantially straight line longitudinally movement to close and open said air gap, said plunger and said core forming a substantially rectangular magnetic frame structure when said air gap is closed, one of said links having a shoulder disposed to engage said abutment to provide a lower limit stop for said plunger, means for pivotally attaching said links to said plunger within said second pair of slots, means for pivotally attaching said links to said core within said first pair of slots, and an energizing winding arranged beneath said pole face to enclose said air gap and a portion of said plunger.

5. An electromagnet comprising a divided stationary core of magnetizable material of substantially O shape having an overhanging upper horizontal leg forming a pole face, a recessed plate of magnetic material disposed between the halves of said core to space said halves apart and thereby to define a first pair of slots, said plate being provided with a mounting flange extending beyond said core and being also provided with a protruding abutment lying at the base of one of said slots, a shading coil of electric conducting material embracing a section of said core and passing through said core and said abutment, a movable plunger of magnetizable material disposed in a position beneath said pole face to define therewith an air gap, the opposite ends of said plunger being centrally recessed to form a second pair of slots, a pair of swingable links movable within said first and second pairs of slots for supporting said plunger in said position and for substantially straight line longitudinal movement to close and open said air gap, said plunger and said core forming a substantially rectangular magnetic frame structure when said air gap is closed, one of said links having a shoulder disposed to engage said abutment to provide a lower limit stop for said plunger and being also provided with an apertured ear extending beyond said core for connection to an external load in pushing relation, means disposed within said first pair of slots for pivotally and detachably mounting said one link upon said core and for pivotally mounting the other of said links permanently upon said core, and means disposed within said second pair of slots for pivotally connecting said one link permanently to said plunger and pivotally and detachably connecting said other link to said plunger, an energizing winding arranged beneath said pole face to enclose said air gap and a portion or said plunger, and a wedge removably positioned between said energizing winding and the lower horizontal leg of said O-shaped core for firmly holding said energizing winding in position.

6. An electromagnet comprising a stationary core of magnetizable material of substantially c shape having an overhanging upper horizontal leg forming a pole face, a movable plunger of magnetizable materlaldisposed in a position beneath said pole face to define therewith an air gap, means for supporting said plunger in said position and for substantially straight line move ment to close and open said air gap, said means comprising a plurality of links pivotally mounted upon said core and pivotally attached to said plunger, a spring attached to said plunger and arranged to bias the lower end of said plunger away from the lower horizontal leg of said c-shaped core in a direction substantially at right angles to the direction or movement of said plunger, and an energizing winding disposed in magnetizing relation to said core and plunger.

7. An electromagnet comprising a divided staextending beyond said core and being also provided with a protruding abutment lying in the base of one of said slots, a shading coil of electric conducting material comprising a U-shaped portion embracing a section of said core and a rivet passing through said laminated core and said abutment and electrically connecting the,

ends of said U-shaped portion, a movable plunger of magnetizable material disposed in a position beneath said pole face to define therewith an air gap, the opposite ends of said plunger being centrally recessed to form a second pair of slots, a pair of swingable links movable within said first and second pair of slots for supporting said plunger in said position and for substantially straight line longitudinal motion to close and opensaid air gap, said plunger and said core forming a substantially rectangular magnetic frame structure when said air gap is closed, one of said links having a shoulder disposed to engage said abutment to provide a lower limit stop for said plunger and being also provided with an apertured ear extending beyond said core for connection to an external load in pushing relation, means disposed within said first pair of slots for pivotally and detachably mounting said one link upon said core and for pivotally mounting the other of saidlinks permanently upon said core, and meansdisposed within said second pair of slots for pivotally connecting said one link permanently to said plunger and pivotally and detachably connecting said other link to said plunger, a springtattached to said plunger and arranged to bias the lower end of said plunger away from the lower horizontal leg of said core in a direction substantially at right angles to the direction of movement of said plunger, an energizing winding arranged beneath said pole face to enclose said air gap-and a porfirst central slot, said core being of substantially C shape to provide a pair of substantially paral, lel extending legs, the ends of said legs "being; arranged to provide pole faces lying in substan, tially perpendicular planes, a movable plunger of magnetizable material centrally recessed to de-, fine a second slot and disposed to complete a magnetic flux path between said pole faces, one end of said plunger defining with a first of said pole faces a variable air gap and the other end of said plunger being disposed adjacent the sec-c 0nd of said pole faces to define therewith a substantially fixed air gap, means for supporting said plunger from said core for substantially straight line movement toward and away from said first pole-face and laterally with respect to said second-face, said means comprising a swingabl-e link movable within said slots and mounted upon pivots on said core and plunger, resilient means for biasing said other end of said plunger away from said second pole face thereby to oppose the magnetic attractive force exerted by said second pole face upon said other end of said plunger in a direction transverse to the direction of motion of said plunger and to minimize the retarding frictional forces at said pivot, and an energizing winding disposed in magnetizing relation to said core and plunger.

ALLEN-G. STIMSON. 

